1. Field of the Invention
This invention relates generally to wind shear detection systems, and more particularly to airborne wind shear detection systems for alerting the pilot of a wind shear condition if the aircraft penetrates a wind shear condition of sufficient force to pose a hazard to the aircraft
2. Description of the Prior Art
Various wind shear detection systems are known. Among these include ground based systems such as systems that utilize a plurality of wind speed and direction measuring stations placed about an airport in conjunction with a system for analyzing the magnitude and direction of the wind at the various stations to provide an indication of a wind shear condition. Other ground based systems utilize Doppler radars located at airports
Airborne systems are also known. Among such systems are systems that compare air mass derived parameters such as air speed with ground speed derived from a radar system. In the event of a rapid change in air speed relative to ground speed, a wind shear condition is indicated. Other systems compare air mass derived signals with inertially derived signals to generate a signal representative of wind shear when the rate of change inertially derived parameters meters varies from the rate of change of air mass derive parameters by a predetermined amount. Two such systems are disclosed in U.S. Pat. Nos. 4,012,713 and 4,079,905. Both of these patents disclose systems that compare a longitudinal accelerometer signal that has been corrected for the effect of gravity with an air speed rate signal and provide a wind shear signal when the difference between the accelerometer derived and the air speed derived signals exceeds a predetermined amount. The '905 patent also takes into account a downdraft drift angle that is a function of vertical acceleration and air speed. Still other systems monitor the rate of change of deviation from a glide slope beam or an ILS beam to provide a signal representative of wind shear.
While all of these systems do provide some indication of wind shear, the ground based systems are responsive only to conditions in the vicinity where the transducers are placed, and are not responsive to dangerous types of wind shear such as microbursts which form and dissipate rapidly.
While airborne wind shear protection systems are more responsive to conditions in the vicinity of the aircraft than are ground based systems, many of them require Doppler radar or signals such as inertial navigation signals, glide slope signals and other signals that are not available on older aircraft. In addition, it is desirable to develop warning criteria which provide a signal that is a measure of wind shear, determine when a wind shear is hazardous without generating excessive nuisance warnings and provide guidance for the pilot when responding to a wind shear indication.